Vibration reduction system for an electric motor

ABSTRACT

A structured product family of dynamoelectric machines for use in a plurality of applications has a frame with a closed end, and a set of permanent magnets is adhesively secured within the frame. An armature disposed in the frame for interaction with the permanent magnets includes a shaft, a core having a set of winding receiving slots therein, and a commutator. During manufacturing and assembly, stress on the motor shaft and commutator is minimized. A brush plate is associated with the frame for locating a set of brushes relative to the commutator, and an end shield is secured to the frame opposite its closed end. At least one freely aligning bearing assembly disposed in the end shield for freely aligning the shaft and including a bearing and a retainer having predetermined conditions preset with the retainer being adhesively secured to the end shield. A bracket is adhesively secured to the frame for connecting the dynamoelectric machine in anyone of the applications; and a novel brush assembly is provided.

This is a divisional of application Ser. No. 08/038,218 filed Mar. 29,1993 now U.S. Pat. No. 5,358,341, which is a divisional of Ser. No.07/805,080 filed Dec. 11, 1991 now U.S. Pat. No. 5,237,231, which is adivisional of Ser. No. 07/423,827 filed Oct. 19, 1989 now U.S. Pat. No.5,113,104.

BACKGROUND OF THE INVENTION

The present invention relates to small motors and methods of making thesame and, more specifically, to a structured product family of motormodels that utilize a maximized number of common, optimized, multipleapplication, cost minimized, components in a cost minimizedmanufacturing process for utilization in a plurality of differentapplications, including automotive applications.

Traditionally, in industries using electric motors such as for examplethe automotive industry, each specific motor application required aconsiderable number of individual components with few, if any, commoncomponents between applications. For example, there typically weredifferent motors for each model of automobile and within automobilemodels, there typically were different motors for heater only blowersystems or air conditioning blower systems and for front wheel drivemodels as well as some rear wheel drive models, there was typically adifferent motor for the radiator cooling fan.

One specific example of this in the automotive industry was the practiceof utilizing three components for the motor frames, a base component, arear end shield component, and a combined unitary front endshield-mounting flange component. This particular practice resulted inseparate tools for each different end shield-mounting flange integralcombination for each application which required a different axialposition of the mounting flange relative to the motor frame. Tools forthe combined integral end shield-mounding frame were quite expensive.

Thus, at least one major automotive manufacturer, it was conventional tohave nearly as many sets of motor manufacturing tooling as there weredifferent motor applications. This conventional system was wasteful ofresources in that it required repetitive, short duration production runsusing a plurality of tooling, thereby raising the unit cost of producingthe required number of different motors to an unacceptable level.

Thus, in order to reduce costs and manufacturing complexities, it isdesirable to develop a "structured product" motor having a minimizednumber of total components which with minor component and manufacturingvariations could be used to produce motors for a maximized number ofdifferent automotive applications that are capable of operating withminimum noise, highly durable, and have substantially lower unitproduction cost.

The brush assembly plates for motors and generators alike vary indesign, but in general comprise boxes to house the brushes, spring meansto apply pressure to the brushes to urge them against the commutator,electrical leads to provide a current path to the brushes and a mountingsurface holding these elements that also provides a means to secure theentire assembly to the motor in such a manner as to place the brushes ina proper working relationship with the commutator.

The useful life of electrical motors that typically find applications inappliances, tools, and automotive vehicles, as well as many industrialapplications, is usually a function of the length of the carbon brush,brush rate of wear, and, in the case of replaceable brushes, the numberof times the brushes can be replaced before the commutator begins toseverely wear.

It is known that the rate of wear of the brushes is a function of theload, the speed of the motor, and more importantly, the spring pressurethat is applied to the brush to keep it in bearing contact with thecommutator. Accordingly, it will be appreciated that with too muchspring pressure, the mechanical wear of both the brush and commutatorwill become excessive, a film having undesirable characteristics isformed on the commutator, and the brush life markedly falls. On theother hand, with too little pressure applied, the electrical arcing dueto the high contact resistance and the mechanical abrasion due to brushcommutator surface bounce greatly reduces potential brush life bydestroying the brush and the commutator surface.

A typical automotive motor brush configuration comprises a helicalspring bearing on the carbon brush, the two elements being contained ina box-like holder such that the brush is urged against the commutator.Although this design is commonly utilized, it has limitations.Specifically, the pressure produced by a helical spring is a function ofits compression or extension. Therefore, when the brush assembly is new,and the brushes are at their maximum length, the spring is at itsfullest compression and the pressure therefore is at its highest. At theend of the brush life, the spring extension is at its greatest and thepressure now on the commutator is below that desired. Therefore,depending on the spring rate, only a portion of the brush wear is in theoptimal spring pressure range.

The conventional motor brush spring used in automotive applicationstends to have a nonconstant force. In other words, the harder and thefurther you pull the spring back, the harder it pushes on theresistance. Thus, if the spring is moved a short distance from itsnormal at rest position, there will be a relatively lower forcegenerated by the spring against the resistance. The further you move thespring away from its at rest position, the greater the force exerted bythe spring against the moving force. However, in applying pressure tobrushes on a brush box assembly plate, it is desirable that a constantforce be exerted against the brush urging the brush against thecommutator throughout the life of the brush and especially after initialwear in.

An additional problem with conventional motor brush springs inautomotive applications is the space they occupy. Specifically, there isonly so much space available within the motor frame to house all of themotor components. Conventional spring means such as coil springs take upvaluable space in the brush area.

With regard to a conventional helical spring which has a finitecollapsed length and which is generally enclosed in the brush boxlocated behind the brush, the space required by the collapsed springnecessitates that a shorter brush per length of brush box be used.

Thus, it is desirable that a spring means be developed which not onlydevelops a rather constant force, but also occupies minimum space inorder to allow the brush sizes to be increased and increase the life ofthe motor.

In certain applications, in order to overcome these shortcomings, aribbon spring that is essentially wound like a clock spring and is setto unwind in such a direction as to hold the brush against thecommutator has been utilized. Since ribbon springs have an essentiallyconstant force, the ideal pressure range can be obtained therebyobtaining optimum contact between the brush and the commutatorthroughout the life of the brush.

With the ribbon spring, the coils providing the engaging force aremounted outside of the brush holder on either side thereof and henceonly a thin ribbon section of the spring is located in the brush boxbehind the brush. Consequently, this configuration provides extra spacefor a longer brush and hence results in the much desired longer brushlife.

However, problems have arisen with brush box/ribbon spring designs inthat occasionally erratic brush life results due to the fact that thewalls confining the spring coil portions tend to impede brush movementin the box perhaps because of vibration in the back and forth motion ofthe brush and the unwinding rotation of the coil portions. Brushimpediment may also be due to the coil portions riding back and forth,or in and out, as well as dereeling in their receptacles.

It is known and appreciated that it is essential that the brush followthe commutator at all times. However, no matter how well or fine thecommutator, the shaft, and the bearing surfaces are machined, someeccentricity will remain in the motor. Accordingly, it is very importantto maintain not only the spring pressure, but also a large degree offreedom of movement of the whole system connected to the brushes.

With conventional designs utilizing ribbon springs, there is a tendencyfor the brush to hit the brush box wall and drag on the bottom or floorthereof. Accordingly, debris such as carbon, dust and the like tends tobe deposited in these areas which further tends to reduce the freedom ofthe system to move.

Brush boxes designed to overcome these shortcomings, such as thosedisclosed in U.S. Pat. No. 4,800,313 to Warner et al., involved thearrangement in which the outer wall of the receptacle or brush box waseliminated and at least two semicircular surfaces were provided forestablishing point or line contacts with each ribbon spring coilportion.

While this system did somewhat solve the difficulties involved with theapplication of the ribbon spring design, a need still remained for asimplified brush box ribbon spring system which: would increase thebrush life by providing the essentially constant force of the brush onthe commutator once the entire brush was in contact with the commutator;would virtually eliminate the tendency of the brush to become hung up inthe brush box due to debris, such as residue, carbon, dust and the like;and keep the coils of the ribbon spring relatively free to rewind towardtheir at rest conditions without binding or being impaired by anycomponent of the brush box or the debris from the system as the brushwears against the commutator.

One of the popular brush plate designs, especially for small fractionalhorsepower motors, utilizes a molded brush plate member of a one-piececonstruction formed from a high temperature resistant plastic which iselectrically nonconductive. The member has the brush boxes formedthereon as well as various openings for securing it to the motor housingand for receiving an extending armature shaft having a commutatorsecured thereto.

A source of noise in the conventional automotive small electric motorhas been the brush. Specifically, the interaction between the brush andthe commutator has generated a considerable amount of noise because ofthe shape of the brush itself. Specifically, one source of noise is theedge of the brush catching in the commutator slots, thus not onlyresulting in noise, but also in momentary increases in the currentdensity as the brush skips a little over the commutator when the brushis caught in the slot.

An additional source of noise in the conventional electric motor hasbeen transmitted through the brush box assembly plate to the frame.Specifically with a rigid connection between the plate and the frame,vibrations generated between the brush and the commutator transmitted tothe plate and then to the frame have produced an unacceptable level ofnoise in the conventional design.

Thus, it is desirable to develop a connection between the brush assemblyplate and the frame which reduces and isolates the vibrations generatedby the brush commutator interaction and which are transmitted to theframe.

Generally, in prior bearing systems utilized in motors for automotiveapplications, automatic self-aligning bearing material which is heldunder the effect of resilient force by allowing a plurality of pawlsformed on a metal holder or retaining plate to come in pressure contactwith the outer peripheral surface thereof has been employed. It is knownthat the alignment torque required for the purpose of self-aligning ofthe ball metal increases correspondingly as resilient force on the pawlsincreases. Accordingly, it is preferable that the resilient force of thepawls be reduced in order to assure that automatic self aligning iseffected smoothly.

However, when the resilient force of the pawls is reduced, they cannotsatisfactorily oppose a load exerted on the ball metal in the radialdirection or in the axial direction, resulting in a nonreliablesupporting function being maintained. Thus, it is preferable that theresilient force of the metal holder be kept low in order to have areduced alignment torque, while it is also preferable that it be kepthigh in order to satisfactorily oppose a load exerted on the ball metal.Accordingly, the resilient force of the metal holder is required to havetwo contradictory characteristics. However, since the conventional metalholder was so constructed that each of the pawls had the same resilientforce, it couldn't have both the high and the low resilient forcesrequired.

In view of the above, the existent state relative to the metal holder issuch that reliable shaft support is considered first and the function ofsmooth self-aligning is somewhat sacrificed. Consequently, the alignmenttorque required for the ball metal is increased and thus the desiredself-aligning cannot be easily achieved. Another drawback is that whenthe metal holder is so fitted that the pawls have a predeterminedresilient force, it has a narrow range of adjustment and satisfactoryfitting is achieved only with much difficulty.

Other attempts to overcome these shortcomings have included providing aholding device for an automatic self-aligning ball metal of which theouter peripheral surface is spherical, the ball metal being adapted tobe held by means of metal holder, wherein the metal holder is formedwith at least two kinds of pawls having a different intensity resilientforce. The pawls having a lower intensity of resilient force come intocontact with the outer peripheral surface of the ball metal earlier thanthose having a higher intensity of resilient force in order toresiliently hold the ball metal.

The pawls extend in the radial direction inwardly of an area located inthe proximity of the outer periphery thereof. The pawls having a lowerintensity of resilient force and the pawls having a higher intensity ofresilient force are alternately arranged in the peripheral direction ofthe metal holder.

Usually the pawls having a higher intensity of resilient force have awidth wider than those having a lower intensity of resilient force.Alternatively, the pawls having a higher intensity of resilient forcemay be thicker than those having a lower intensity of resilient force onthe assumption that they have the same width.

Bearing retainers constructed in the above described later developedmanner whereby the resilient holding force exerted on the bearing by theretainer functions weakly at the time of automatic self-aligning, butfunctions intensely when there's a load applied to the ball metal in theaxial direction, are shown in U.S. Pat. No. 4,806,025, issued Feb. 21,1989, to Kamiyama, et al. While the automatic self aligning bearingsdescribed in the above patent were advances over the known art,solutions to the problems of repeatability and the amount of forcerequired to align the bearings have remained elusive.

In conventional motors having permanent magnet field poles, reluctancetorques are introduced during rotation of rotary errantries under thepoles. The reluctance torque is a position-sensitiveperiodic-with-rotation torque which occurs in the absence of excitationof the armature. Occurrence of this torque is due to the interaction ofthe permanent magnet field and the slots in the armature. Because ofthese slots, the reluctance of the magnetic flex varies at differentpoints around the armature. This means that the magnetic energy in theair gap field between poles and the armature is not uniform at allpoints circumferentially around the armature. This occurrence ofreluctance torque is manifested by pulsations, throbbing andirregularity in rotational speed which are objectionable at allrotational speeds, but are most noticeable and objectionable at lowspeeds. Previously, attempts have been made to reduce reluctance torquein direct current motors by such means as for example skewing thearmature slots. However, skewing adds complexities to the armaturemanufacturing process.

The reluctance torque phenomenon occurs inherently in all energizedmotors which have a change in the air gap as a function of rotation. Itis desirable to control reluctance torque especially in automotiveapplications while minimizing the number of different componentsnecessary to accomplish the maximum number of applications andminimizing product and process cost and complexities.

Another problem with prior conventional motors, especially thoseutilized for automotive radiator cooling applications, has beendurability. Specifically, one motor design failed after approximately500 hours of usage which roughly corresponds to 40,000 miles ofautomobile driving. These prior motors failed primarily because themotor brushes had been used up. Thus, in order to extend the usefulmotor life used in such an application, it is desirable to extend thebrush life.

Another determined shortcomings of this prior motor utilized as aradiator cooling motor was bearing failure possibly due to bearinglubrication failure. Thus, it would be desirable to develop alubrication system or a bearing system for the motor which extended thelife of the bearing systems.

Accordingly, there is a need for an improved motor and methods of makingthe motor and its various components. Such a motor should be astructured product utilizing a minimum number of components toaccomplish a maximum number of different applications includingautomotive applications and should: produce significantly reduced noiselevels in comparison to prior motors especially those for automotiveapplications; have a predetermined set of conditions preset in at leastone bearing system which is repeatedly duplicatable in a plurality ofother individual bearing systems; have an improved brush card assembly;have precisely contoured and beveled brushes which significantly reducethe noise produced by the brush/commutator interaction; have preciselydimensioned and aligned brush boxes; have a brush box/brush platecombination which significantly reduces stresses in the plate; have thelaminations assembled to the shaft such that a minimum amount of stressis applied to the shaft; have a commutator assembled to the shaft suchthat a minimum amount of stress is applied to the commutator itself orto the shaft; have an armature which is first rough finished, balanced,and then final finished to insure precise dimensional tolerancesbalance; have oil slingers which are part of the armature; have a stiffend shield which reduces the noise produced by the motor; have preciselydesigned and contoured magnets and precisely designed laminations whoseinteraction reduces reluctance torque; and have an adhesively mountedflange/frame combination which significantly reduces the noise producedby the motor and reduce tooling costs.

SUMMARY OF THE INVENTION

In carrying out the present invention in preferred forms thereof, weprovide a structured product motor for automotive applications andmethods of assembling various sub-components of the motor. Anillustrated embodiment of the invention disclosed herein, is in the formof a motor intended for use as a motor to power an automotive heaterfan, an automotive air conditioner fan or an automotive radiator coolingfan.

Each structured motor comprises: a frame having bearing receiving meansand at least two magnet means operatively adhesively positioned therein;armature means including a core formed from a plurality of laminations,a shaft and commutator means having slots, operatively positioned in theframe, for interacting with the magnet means; brush plate assemblymeans, operatively connected to the frame, for precisely locating atleast two brush means relative to the commutator means; conductor means,operatively connected to the brush means, for conducting electricity;end shield means having bearing receiving means operatively connected tothe frame, for enclosing the machine; at least one freely aligningbearing means, operatively positioned in at least the end shield bearingreceiving means, the bearing means having a set of predeterminedconditions preset therein and held by the adhesive means; mountingflange means, operatively adhesively connected to the frame, foroperatively connecting the machine to anyone of a plurality ofapplications, such as automotive applications.

Other aspects of the structured product motor which contributes to itsimproved performance and cost advantages when compared to prior motorsinclude the following structural and functional features.

The structured product motor further comprises an open and a closed end,the open end having end shield positioning means and isolator mountingmeans operatively formed therein, the closed end having a plurality ofcooling means operatively formed therein so that noise transmissiontherethrough is reduced.

The frame bearing means can have either a ball bearing or a sleevebearing with retainers, operatively positioned in the frame bearingreceiving means, for operatively interacting with the shaft, the sleevebearing retainer being adhesively held in position in the bearingreceiving means after the establishment of a predetermined set ofconditions therebetween, the same predetermined set of conditions beingrepeatedly duplicated in a plurality of different sleeve bearing meansin a plurality of different bearing receiving means despite dimensionalvariations in each different bearing, each different retainer and eachdifferent bearing receiving means.

The two magnet means additionally have, when assembled in the frame,gaps therebetween and are positioned in the frame so that noise,generated inside the frame and transmitted between the gaps toward theclosed end of the frame, exiting the frame through the plurality ofcooling means is significantly reduced.

The shaft is approximately precisely uniform and has a bearing surfaceat one end and an application connector means at the other, a pluralityof laminations having slots, forming a core are inductively heated priorto being operatively positioned on the shaft.

A spacer is operatively positioned on the shaft between the bearingsurface and the lamination core.

Insulating means are operatively, uniformly distributed over thelamination core, the spacer and at least a portion of the shaft.

The commutator comprises an inner insulating core portion and an outerelectrical conduction portion, preferably made of copper, having slotsand tangs, the commutator being operatively adhesively bonded to anuninsulated portion of the shaft between the bearing surface end and thelamination core.

Conducting means, such as magnet wire, is operatively wound in thelamination slots and is operatively connected to the commutator tangs.

Each oil slinger comprises a cup shaped portion for slinging oil backinto the bearing means.

An end play compensation means is operatively positioned between the cupshaped portion of one oil slinger and the commutator, for adjusting theend variation of the shaft to within a predetermined range.

An axial vibration reduction means or thrust compensation systemcomprising at least one, preferably elastomeric, washer and at leastone, preferably nylatron, washer, with one of the preferably elastomericwashers being operatively positioned adjacent the oil slinger mostproximate the spacer and another preferably elastomeric washer beingoperatively positioned adjacent the oil slinger most proximate thecommutator. The armature is preloaded or biased by positioning themagnet means, relative to the core, more proximate the closed endportion of the frame so that the interface between the bearing surfaceand at least one nylatron washer of the thrust compensation means willcause pressure on the adjacent bearing means. This preload results fromthe natural tendency of the magnets to axially center the laminationcore so that the axial vibration/movement of the armature issignificantly reduced.

Each brush is precisely formed with a bevel for contacting thecommutator and each brush has an electrical connector means, such ascopper pigtails, operatively connected thereto.

The brush plate assembly means include a plate and preferably has atleast eight D-slots operatively formed therein and at least threeisolator means operatively connected thereto.

At least two brush boxes are operatively connected to the brush platepreferably utilizing the D slots as connecting means for minimizingstress in the plate and for precisely positioning the brushes normal tothe outer surface of the commutator.

A ribbon spring, operatively connected to each brush, urges each brushagainst the outer surface of the commutator at an approximately constantforce per unit area of contact therebetween.

An electrical conductor means, such as a plug, is operatively connectedto the brush connector means, such as a copper pig tail, for conductingpower to and from the motor.

The end shield further comprises electrical conductor receiving means,corresponding to the electrical conductor positioning means of the openend of the frame, isolator retaining means, corresponding to theisolator mounting means in the open end of the frame, and bearingreceiving means for receiving a freely aligning bearing means therein,the freely aligning means being adhesively held in position in thebearing receiving means after the establishment of a predetermined setof conditions therebetween, the same set of preconditions beingrepeatedly duplicated in a plurality of individual bearing means in aplurality of individual bearing receiving means despite dimensionalvariations in each individual bearing, each individual retainer and eachindividual bearing receiving means.

Each mounting flange comprises a mounting portion having a centralaperture and a plurality of mounting means formed therein, and a cupshaped portion having an upper and a lower end and an inner and an outersurface, operatively connected to the central aperture at its lower end,the radius of the upper end being greater than the radius of the lowerend, the surface of the cup shaped portion between the upper and thelower end gradually decreasing from a maximum at the upper end radius toa minimum at the lower end radius, the upper end portion having a lipportion so that when any one flange is operatively positioned on theframe, the cup shaped portion forms a reservoir for receiving anadhesive, for interacting with an adhesive activator applied to theinner surface of the cup shaped portion and/or the outer surface of theframe whereby the flange and the frame are adhesively bonded together.

The specific illustrated structured product motor developed for aspecific automobile model includes: two frames differing only in axiallength; three different magnets, two having the same tapered end anddiffering only in axial length and the other magnet having no taper; aplurality of different shafts each differing in its application end withsome differing in length and others differing in diameter; a singlelamination utilized in two different stacks to form a core; twodifferent commutators, a single preferred brush card assembly platehaving two different brush boxes mounted thereon and two differentbrushes, one for each different brush box; a ribbon spring mounted ineach brush box for urging each brush toward the commutator selected fromtwo different springs according to the end application; two bearingsystems, one freely aligning sleeve bearing system utilized in both theframe and the end shield and one ball bearing system utilized in theframe only, a single spacer operatively connected to the shaft; oneisolator means for interconnecting the brush plate assembly with theframe; one oil slinger mounted on each end of the shaft, one proximatethe spacer and the other proximate the commutator, although in oneapplication, only the oil slinger approximate the commutator isutilized, and a single end shield for all applications; one of twopossible plugs selected according to the end application and a mountingflange for each application.

Other aspects of the present invention include methods for: adhesivelyconnecting the magnets to the frame, adhesively connecting thecommutator to the shaft, adhesively positioning and establishing apredetermined condition in a freely aligning bearing means in both theend shield and the frame, and adhesively connecting the mounting flangeto the motor frame.

Accordingly, objects of the present invention include: to provide astructured motor comprising a maximum number of common, cost optimized,motor subcomponents combined to accomplish the maximum number ofapplications including automotive applications; to provide a motorhaving minimum tooling cost; to provide a motor having minimummanufacturing costs; to provide a motor which generates a minimum amountof noise; to provide a motor having reduced reluctance torque; toprovide a motor having at least one freely aligning bearing system; toprovide a motor having relatively constant contact pressure between thebrush and the commutator surface throughout the life of the brush; toprovide a motor having a one piece formed frame which includes onebearing socket; to provide a motor having oil slingers which form partof the armature assembly; to provide a motor having a single computeroptimized lamination design for a plurality of different applications;to provide a motor having laminations forming the core secured to theshaft by an inductive heating process; to provide a motor having thearmature balanced prior to the commutator being final finished; toprovide a motor having a brush plate assembly which generates less noisethan prior known motors for automotive applications; to provide a motorhaving the brush boxes precisely located on the brush plate so that theinteraction between the brush and the commutator generates less noisethan prior motors for automotive applications; to provide a motor havingextended brush life; to provide a motor having reduced brush lock-ups inthe brush box; to provide a motor having a brush that does not catch inthe commutator slots; to provide a motor having a brush which rapidlyseats on the commutator; to provide a motor having a freely aligningbearing means with predetermined conditions preset therein; to provide amotor having a freely aligning bearing means having predeterminedconditions which are repeatedly duplicated in a plurality of individualcomponents despite dimensional variations in the various individualcomponents making up the bearing means; to provide a motor havingimproved bearing life; and to provide a motor which has a plurality ofmounting flanges adhesively bondable for a plurality of differentapplications.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a exploded perspective view of a structured product motor thatembodies the present invention in one form thereof;

FIG. 2A is a sectional view with portions cut away of the motor of FIG.1;

FIG. 2B is a partial sectional view of FIG. 2A illustrating the ballbearing system utilized for engine cooling applications;

FIG. 3A is a sectional view of the magnet utilized for air conditioningapplications in the motor of FIG. 1;

FIG. 3B is a cross sectional view of the magnet utilized for enginecooling fan applications in the motor of FIG. 1;

FIG. 3C is a cross sectional view of the magnet utilized for heaterapplications in the motor of FIG. 1;

FIG. 4A is a sectional view of a partially constructed armature of themotor of FIG. 1;

FIG. 4B is an end view taken along line 4B--4B of FIG. 4A,

FIG. 5 is a plan view of the laminations utilized in the motor of FIG.1;

FIG. 6 is sectional view of the cup shaped portion of the oil slingersutilized in the motor of FIG. 1;

FIG. 7 is a plan view of the brush card assembly plate of the motor ofFIG. 1;

FIG. 8A is a partial plan view of the brush box showing the ribbonspring in position in the brush box of the motor of FIG. 1;

FIG. 8B is an end view of the brush box of the motor of FIG. 1;

FIG. 9A is a plan view of a representative brush utilized in the motorof FIG. 1;

FIG. 9B is a side view of the brush of FIG. 9A;

FIG. 10A is a plan view of the inside portion of the end shield of themotor of FIG. 1;

FIG. 10B is a sectional view taken along line 10B--10B of FIG. 10A;

FIG. 11A is a plan view of the freely aligning bearing system of themotor of FIG. 1;

FIG. 11B is a section view of the freely aligning bearing system of FIG.11A taken along line 11B--11B,

FIG. 12A is a side view with an alternate mounting flange in section ofthe motor of FIG. 1; and

FIG. 12B is an end view of the motor of FIG. 12A taken along line12B--12B with portions cut away for clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENT Combination Summary

One embodiment of the motor of the present invention illustrated as astructured product permanent magnet motor for a plurality of automotiveapplications, generally designated as 20, is illustrated in FIGS. 1-12B.This specific motor 20 comprises a frame 22 having at least twoapplication specific permanent magnet means 24 operatively positionedtherein for functioning as the stator component of the motor 20; anarmature means 26 (FIGS. 4A and 4B) having a core 28 of specificallydesigned laminations 30 which, in combination with the magnet means 24,provides a low reluctance torque, operatively connected to a precisionformed shaft means 32 by a heat induction process; a specificallydesigned commutator means 38 operatively positioned on the shaft 32;brush plate assembly means 40 for isolating vibrations from the frame 22and for aligning brush boxes 42, 44 on the plate means 40 in such a waythat the motor has improved durability and reduced noise. The brushplate assembly 40 includes brush means 48 which are operativelypositioned in the brush boxes 42, 44, the brushes being urged againstthe commutator means 38 by ribbon spring means 50; a stiffened endshield 54 for enclosing the armature means 26 within the frame 22 andfor raising the natural frequency of vibration produced by the motor 20;at least one freely aligning bearing means 60 operatively positioned inthe end shield 54 and optionally in the frame 22 for aligning the shaft32; and a plurality of specific application mounting flanges 64, 64'each operatively adhesively connected to the frame for positioning themotor 20 for each different application, some of the mounting flangeshaving stiffening ribs 66 (FIG. 12B) for reducing vibrations by raisingthe low natural frequency up so that motor structure noise issignificantly reduced.

Frame

As shown in FIGS. 1, 2A, 2B, 12A and 12B the unitary or cup-shaped frame22 of the illustrated embodiment is generally cylindrical inconfiguration and houses permanent magnets 24 which are preferably ofcurved, rectangular configuration.

The closed end portion of the frame 22 has a protuberance 68 with anaperture 70 formed therein for receiving the shaft 32. This protuberance68 has a bearing socket 71 which receives freely aligning bearing means60, (FIG. 2A), utilizing a sleeve type bearing for heating and airconditioning applications and preferably a ball type bearing means 60'for engine cooling applications (FIG. 2A), the details of the bearingmeans 60, 60' will be discussed below.

A plurality of cooling apertures 72 (FIG. 1) are formed in the closedend portion of the frame adjacent protuberance 68 for motor coolingpurposes. In order to achieve improved noise reduction, coolingapertures are omitted in the end of the frame adjacent protuberance 68in the areas 74, 76 roughly corresponding to the gaps 78,80 between thepermanent magnets 24 because it has been determined that noise has atendency to travel down the gaps 78, 80 between the magnets 24 and outthrough any cooling apertures 72 which might be positioned correspondingto the gaps 78, 80.

In an effort to minimize the number of separate components of theillustrated embodiment, the gaps 78, 80 between the magnet and the area74, 76 do not correspond exactly in any of the specific illustratedmotor embodiments. This is due to the different locations of the magnetswith reference to their position within the frame due to the differentdirection of turning or rotation of the shaft relative to the frame.Thus, there is, although ideally not preferred, in practicalapplication, a small portion of one of the apertures 72 which overlapsthe gaps 78, 80.

The frame 22 also has an aperture 82 (FIG. 2A) positioned therein forthe reception of a conduit (not shown) which will allow cooling air tobe drawn through the inner portion of the cup shaped frame and over thearmature means 26. The aperture 82 works in conjunction with the framecooling apertures 72 to facilitate the flow of cooling air within theillustrated motor 20.

The location of the aperture 82 (FIG. 2A) relative to the brush plateassembly 40 is important and is selected so that air entering theaperture 82 is directed to flow over the brush boxes and brushescontained therein thereby somewhat cooling those components.

A plurality of end shield positioning means and isolator mounting means,such as for instance cutouts 84, 86, 88 are formed in the open end 90 ofthe frame 22 for receiving a plurality of, preferably resilient,isolator means or grommets 94 for operatively connecting the brush plateassembly means 40 to the frame 22. An additional rectangular shapedcutout 96 is formed between two of the brush plate assembly isolatorreceiving cutouts 84,86 for receiving an electrical connector or plug 98therein.

As with any real-life project, the application which led to thedevelopment of the illustrated motor involved certain physicalconstraints. Specifically with regard to the frame, the area availableto house the motors for the various applications constrained the motordiameter to no more than approximately 76 millimeters. This constraintin overall outer motor diameter established the initial motor designparameters.

As is well-known, the frame is required to carry the magnetic flux andis sized so the frame is at the edge of the saturation per minimumthickness so that the frame can carry the needed amount of flux butwithout excessive material being contained therein. Thus, given thediameter constraint of the illustrated motor, the thickness of the frameand the length of the frame, length being defined as the distancebetween the air gaps cooling aperture 72 and the portion of theconductor receiving means 96 most approximate to those coolingapertures, the product thereof must be sufficient to carry the necessarymagnetic flux for the overall system.

In the illustrated motor, the frame was sized as small as possible tofit within the space available and at the same time to have the minimumamount of material contained therein effective to carry the requiredmagnetic flux.

In the illustrated motor, given the three distinct applications, twoframes differing only in length were required to meet both the spaceavailable and the magnetic flux requirements.

Magnets

As shown in FIGS. 1, 2A, and 3A-3C, the magnets 24 utilized with theillustrated motor are made of conventional magnetic material. Themagnets 24 (FIG. 1) have a general arcuate shape which conformsgenerally with the inner surface 120 of the frame 22 (FIG. 2A). Eachmagnet 24 comprises a middle portion 100, two end portions 102,104, anouter surface 106 and an inner surface 108. The outer surface 106 whichcontacts the inner surface 120 of the frame 22 (FIG. 2A) of each of themagnets shown in FIGS. 3A, 3B, and 3C, is formulated according to thetri-arc method. This known method of fabricating permanent magnets whichare attached to the frame wall comprises using two different circleradii to insure that there are at least two points of contact betweenthe magnet and the frame wall. In the magnets utilized in theillustrated embodiment, it is preferred that the points of contact bespaced apart approximately ninety (90) degrees and that each one beapproximately forty-five (45) degrees from the center line of themagnet. These points would roughly correspond to locations 110, 112 inFIGS. 3A, 3B, and 3C.

The magnet frame contact points 110, 112, as is well known, will varyslightly due to variations in the frame and magnet curvatures. Thistri-arc technique is utilized to prevent the rocking of the magnetrelative to the frame. As is known, stability of the magnet, afterplacement of the magnet on the frame, with relation to the armature coreis critical to insure a constant air gap between the core 28 or theouter surfaces of the laminations 30 and the inner surface 108 of themagnets 24. A consistent air gap between the magnets and the laminationsof the armature core is important because reluctance torque is sensitiveto the net air gap between the magnet 24 and the core 28 of the armature26, net air gap being defined as the distance between the inner surface108 of the magnet 24 and the outer surface of the core 28. Cogging orreluctance torque is defined as the torque required to turn the armatureor the torque pulsations to turn the armature 26 when the illustratedmotor 20 is unenergized.

For the air conditioning and the heater fan applications as shown inFIGS. 3A and 3C, the inner surface 108 of the magnet is thicker at thecenter portion 100 and tapers off to the ends or tips 102, 104. Thistaper effect is the result of the inner radius corresponding to theinner surface 108 of the magnet being determined from a different focuspoint 113 then the focus point 114 used to determine the outer radiuscorresponding to the outer surface 106 of the magnet as well as the useof different radii at points 113, 114. The resultant distance betweenpoints 107, 115 is greater than the distance between point 116, on theouter surface 106 and point 117 on the inner surface 108. In general,the thickness of the magnets, as shown in FIGS. 3A, 3C, is greatestbetween points 107, 115 and gradually decreases in either direction fromthe center 100 of the magnet to the tips 102, 104.

The gradual decrease in magnet thickness from the center 100 toward eachtip 102, 104 reduces the cogging or reluctance torque of the motorshaving these magnets operatively positioned therein because the air gapor the distance between the magnets inner diameter and the armature coilouter diameter will increase as you move away from the center 100 of themagnet 24, thereby allowing the energy in the air gap to approach moreclosely a more constant value as the armature 26 is rotated.Specifically, the taper provides for a gradual change in flux as the airgap is approached.

The magnet for the engine cooling application, as shown in FIG. 3B, dueto the consistent distance between the outer surface 106 and innersurface 108 has a some what higher reluctance torque so that there ismore flux in the illustrated motor resulting in more efficient motoroperation. In this embodiment, additional reluctance torque is desirableso that the armature 26 does not move as readily when unenergized or asa result of air moving through the radiator (not shown) and through thefan (not shown) connected to the illustrated motor 20. If the air movingthrough the radiator and fan were to cause the fan to rotate orwindmill, oil would be pumped out of the bearing 60 (FIG. 1) proximatethe end shield 54 possibly causing the bearing to fail prematurely.Additionally, as opposed to the heating or air conditioning application,noise caused by vibration resulting from a torque ripple related to thereluctance torque is not as critical because of the other audible noiseunder the hood of an automobile.

The magnets 24 of the illustrated embodiment, working with othercomponents, such as the frame, of the illustrated motor were optimizedfor performance as a function of cost, size, and weight of the motor.Some of the performance specifications of the illustrated motorimpacting upon the magnet design were: motor shaft torque at a specificspeed or rpm; cogging or reluctance torque; upon starting the motor, thecurrent required to demagnetize the magnets at a given temperature (thegiven temperature for the illustrated motor is at or below minus forty(-40) degrees C. with 5% or less demagnetization); maximizing motorefficiency for all applications at the specified ranges for: ambienttemperature; output power; input voltage; etc.; motor size/volume; motorweight; motor noise; durability (bearings, brushes, etc.); andlongevity, among other factors.

Other parameters of the magnets which are varied to reach the optimalcost, weight, and volume versus performance include: outer radius as afunction of the angular magnet span, radial magnet thickness as afunction of the angular span, axial length, angular span, choice ofmaterial composition of magnet, radial air gap as a function of theangular span, and radii at the edge as the magnet tapers. The cost ofthe magnets can be mathematically expressed as a continuous function ofthe physical parameters which are then used to predict magnetperformance. These various parameters, which are all interrelated andinterdependent upon each other, are optimized in order to optimize themagnet performance versus cost.

The magnets 24 are adhesively bonded to the frame 22 according to thefollowing method. First, the outer surface 106 of the magnet 24 which isgoing to contact the frame 22 and the frame inner surface 120 which willbe in contact with the magnet's outer surface have dust, oil and greaseremoved therefrom. After the relevant parts are cleaned, an adhesiveactivator, such as preferred Dymax activator 535 available from Dymax ofTorrington, Conn., is applied to the inner surface 120 of the frame 22which will be in contact with the magnets and the solvents are allowedto evaporate therefrom. Two beads (one bead may suffice) of adhesive,such as preferably Dymax 20012 revision A, are applied to the magnetouter surface 106 at which time the magnets and the frame are broughtinto contact and the adhesive is spread and mixed with the activator.The assembled parts are clamped together for approximately 60 seconds inorder to obtain fixturing strength. The magnets assembled according tothis method should have adhesive which covers a minimum of 85 percent ofthe magnet outer surface area.

Armature

As shown in FIGS. 1, 2A and 4A-6, the armature means 26 utilized withthe illustrated motor 20 comprises: one of a plurality of relativelyuniform, precisely formed shaft means 32 having one end 122 for mountingin the end shield bearing means 60 and having the other end 124 modifiedaccording to the specific application to which the motor is operativelyconnected, such as a blower means for a radiator, air conditioner orheater; a specific number of stacked, inductively heated laminations 30forming a core 28 operatively positioned on the shaft 32; a spacer 126operatively positioned on the shaft 32 proximate the application end 124and a commutator means 38 operatively positioned on the shaft 32proximate the end shield end 122 thereof; winding means, such as magnetwire 125 wound through the various lamination slots 128 and connected tothe commutator means 38 by a plurality of tangs 130; and an insulatingcoat of an epoxy resin 132 (FIG. 4A) applied to the laminations 30,shaft 32 and spacer 126 by an electrostatic fluidized bed coatingprocess (not shown).

Presently, the preferred material for the spacer, nylon 46 has theadvantage of surviving the heat of the epoxy coater utilized to applythe insulation layer.

Laminations

As shown in FIGS. 1, 4B and 5, each lamination 30 comprises a yokeportion 133 and a plurality of lamination teeth 134 having a width T₁.Each lamination tooth 134 includes a rectangular portion 136 and a Tportion 138 on the outer periphery of the lamination. Each laminationtooth T portion 138, has symmetrical tips or portions 140, 142. Each tipportion has a width 143. The slots 128 are formed between two adjacentteeth 134.

The illustrated lamination 30 has the same number of lamination teeth134 as lamination slots 128. The lamination slots have a width 129between tip portions 140, 142 which provide for the introduction ofmagnet wire into each slot 128. In the illustrated lamination, there arepreferably twelve (12) lamination slots and teeth.

The parameters of the lamination design which are varied along withother parameters of the illustrated motor to reach an optimalcombination involving the lamination and the magnet design etc., are:angular width of the tooth slot opening 129, radial width of the toothtip 143, angular span of the tooth at the air gap 135, tooth width T₁,number of teeth (12 in this embodiment), slot area 145, radial depth ofthe back iron or yoke 133, outer diameter of the lamination 147, axiallength of the core 28 (composed of more than one lamination), the magnetoverhang or the axial length difference between the magnet and the core,(FIG. 2A) the inner diameter of the lamination or shaft diameter,lamination material, and lamination thickness 31.

The above mentioned parameters are dependent upon various factors,however, the most basic factor is the amount of flux required and theamount of flux that the lamination steel will carry. It is commonlyknown that steel will carry a certain amount of flux density until itsaturates. At that point, the steel will carry additional flux only witha greatly disproportionate increase in magnetic force than was appliedat lower flux levels so there is a trade-off between the slot area 145versus the amount of available steel, the tooth width T₁ and the yoke133. One important limiting factor relating to the size of the slot 128is the optimization of the slots area 145 for housing the magnet wireverses just barely saturating the steel. The goal is to minimize thetooth width while maximizing the wire housing area 145 and whilemaximizing the amount of flux that the steel can carry.

The outer diameter of the lamination 147 plays a role in laminationoptimization in that it effects the amount of flux that is possiblesince the magnitude of the flux is a function of the diameter of thelamination and the diameter of the motor. Basically if the flux is asclose to saturation as possible or only a little over, there must besufficient area in the wire housing area 145 for the magnet wire. Thesefactors establish the dimensions of the lamination which then establishthe values of the other parameters. All of the above factors areoptimized to minimize the cost and the volume with respect to the outerdiameter of the motor.

With respect to cogging or reluctance torque, the angular width of thetooth slot opening 129 is important in that it should be minimized whileallowing sufficient space for physically winding the magnet wire intothe slots 128. The smaller the slot width 129 the less the reluctancetorque. The tip thickness 143 is also important because as it isincreased, reluctance torque is reduced.

In selecting the lamination thickness 31, it is desirable to have aminimum number of laminations because thicker steel is less expensive.However, the thicker the steel the greater the magnitude of the inducededdy currents. In the illustrated embodiment the lamination thicknesswas optimized as an intermediate between current considerations andsteel cost considerations.

As with the cost of the magnets, the cost of the lamination can also bemathematically expressed as a continuous function of the physicalparameters which are then used to predict lamination performance. Theseparameters are all interrelated and dependent upon one another.

In order to assemble the core 28 on the shaft 32, the laminations 30 arefirst stacked, forming the core 28, inductively heated, placed on theshaft 32 and then cooled so that they are connected to the shaft 32without being distorted as is sometimes caused by press fitting.

The specific method for connecting the core 28 comprising a plurality oflaminations 30 to the shaft 32 of the illustrated motor 20 is asfollows. The specific number of laminations, such as 37, used in oneapplication, are randomized and realigned. Each of the laminations 30will have the slot burrs facing the same direction. End lamination burrsare removed by a bushing operation. Alternatively, an inverted endlamination is placed on the stack so that the slot burrs and the shafthole burrs face inward. The stack height of loose laminations will bemeasured with a 20 pound axial force applied to the laminations. Theweight may be increased if an axial density of at least approximately0.535 pounds per inch results from its applications. The stacked andaligned laminations are now heated to a temperature which will allow theshaft 28 to slip fit into the laminations stack, preferably atemperature between 900 degrees F. but not to exceed approximately 1,200degrees F. unless an inert atmosphere is used in which case thetemperature should not exceed approximately 1,200 degrees F. As theshaft 32 is being inserted, the laminations 30 are pressed together withsufficient force so that the axial density of the core exceedsapproximately 0.35 pounds per inch. This force, while sufficient tocreate that density, must not cause the laminations to spread apart atthe outside diameter of the stack. The outside diameter gap, due tolamination bow, should not exceed 0.18 millimeters. During this process,the laminations 30 are held together until they are tight on the shaft32.

The shaft 32 is inserted into the lamination core 28, preferablycommutator end 122 first, and must not stick during the insertion. Afterinsertion, the laminations 30 should be air cooled and the endlamination must withstand approximately 0.53 newtons--meter or 75oz.--inches of torque without turning. After the assembly, the shaftbearing journals 144, 146 will be checked for marring, and the shaft 32will be checked for straightness. The assembled core should be able towithstand ten times the stall torque of the motor which is approximately2,000 oz-in for air conditioning motors.

Magnet wire 125 is operatively wound in the slots 128 and operativelyconnected to the tangs 130 such as by fusing. After assembly andcommutator rough finish operation, the armature assembly 26 is balancedby adding precise amounts of an epoxy (not shown) to the winding atprecise positions and then the commutator is final finished. Thissequence of steps provides for the precision balancing of the armaturemeans 26 which goes well beyond the levels of balance and commutatorroundness achieved in prior motors used in automotive applications.

One of the key elements of the motor of the illustrated embodiment isthe reduction of the reluctance torque or the torque required to rotatea steel structure inside of a magnetic field, in this case, permanentmagnets. The higher the reluctance torque, the greater the noisegenerated by structural vibration. The motor of the present inventionhas very low levels of reluctance torque and this results from thecombination of frame, magnet and lamination design optimization, asmentioned earlier.

Commutator

As shown in FIGS. 1, 4A, and 4B, the commutator means 38 comprises onecontinuous copper ring or outer electrical conduction portion 148 whichis rolled around an insulator or inner insulating portion 150 and thencut to size. The insulator 50 preferably comprises a phenolic materialhaving an aperture or bore 152 formed therein for receiving the shaft32. Tangs (not shown) are operative to hold the copper ring 148, havinga plurality of slots 154, stationary on the insulator 150. Thecommutator means 38 is adhesively connected to the shaft 32 by applyingthe adhesive activator to the bore 152 surface in the insulator 150.Adhesive is then applied to the shaft 32 and the commutator means 38 isoperatively positioned thereon. The adhesive bond is important in orderto avoid possible commutator or shaft distortion which might result fromconventionally press fitting the commutator to the shaft.

It is important to maintain the dimension tolerance for both the shaft32 and the commutator bore 152 in a well defined range in order toproperly position the commutator 38 on the shaft 32.

When assembled on the shaft 32, the commutators twelve (12) slots 154and the laminations twelve (12) slots 128 which carry the magnet wireforming the coil, must, in order to function properly, be preciselyaligned relative to each other (FIG. 4B). This alignment is accomplishedby a means for positioning the commutator 38 on the shaft 32 in such aposition that the commutator slots 154 are properly positioned relativeto each lamination teeth center line 137 by mechanically coordinatingthe relative positions of the commutator slots 154 to the laminationteeth prior to the setting of the adhesive which secures the commutatoron the shaft.

Since it is important that the commutator 38 be securely and preciselylocated on the shaft 32, the commutator means 38 utilized in theillustrated motor is adhesively connected to the shaft 32 according tothe following method. First, it is important to make sure that thecommutator bore 152 which will be contacting the shaft and the shaftitself are free of dust, oil and grease. Next, an adhesive activatorsuch as preferably Dymax activator 535, is applied to the commutatorbore 152 and the solvents are allowed to evaporate. The commutator isassembled part way onto the shaft so that adhesive will be spread thefull length of the commutator 38, but not spread beyond the commutatorin the area of an oil slinger 156 and bearing journal 144. An adhesivesuch as preferably Dymax 328 VLV is applied to the chamfer on the tangend of the commutator. The commutator and the shaft are rotatedapproximately 90 degrees in order to mix the activator and the adhesiveand allowed to set for approximately one minute minimum. Thereafter, theparts are placed under ultraviolet light for a minimum of two minutes inorder to cure the adhesive bond between the commutator and the shaft.

Oil Slingers

As shown in FIGS. 1 and 6, the oil slingers 156, 158 of the illustratedmotor 20, which previously have been part of the bearing system inconventional automotive DC motors, are part of the armature means 26.Each oil slinger 156, 158 comprises a cup shaped member 160. The oilslingers 156, 158 are operatively positioned on the shaft proximate thespacer 126 and the commutator means 38 respectively. The cup shapedmember 160 has a base member 166 having a bore 168 formed therein and acircular portion 170 having a greater diameter at its outer portions 172and a lip portion 174.

The oil slingers 156, 158 are positioned in the illustrated motor sothat when oil leaks from the bearing, it is directed into the cup shapedmember 160, which is rotating with the shaft 32, and is propelled backinto the bearing 60. This increases the bearing life which when combinedwith the advantages of a freely aligning bearing reduce noise andgreatly extend the motor life.

Prior to the positioning of oil slinger 156 on the shaft 35, an end playcompensation means 175 is positioned on the shaft 32. The end playcompensation means 175 adjusts the play in the shaft to a predeterminedtolerance thereby properly positioning the application end 124 of theshaft.

Thrust Compensation Means

An axial vibration reduction which comprises in part a thrustcompensation means, 177, comprising a first washer means 162, preferablyan elastomeric or rubber washer, and a second washer means 164,preferably a NYLATRON plastic washer is utilized to counter a preloadforce on the frame bearing in socket 71 which is due the greater magnetoverhang or distance between the end of the core 28 and the end of themagnet 24, as shown in FIG. 2A, and that portion of the magnets and coremost proximate the shaft end 124. The amount of magnet overhang isdifferent for each of the three applications illustrated.

The thrust compensation means 177 is utilized to maintain the preload orbiased initial position of the armature relative to the magnets. Thenatural tendency of the armature to be more toward one end, due to themagnet preload, is utilized to maintain pressure on the bearing system60 proximate the application end 124 of the frame 22. This initial biasinduced pressure severely restricts axial movement of the armaturebetween the two bearing means and thus reduces noise which usuallyresults from armature axial movement. Specifically, the intentionalpreload attempts to maintain a single brush/commutator track throughoutthe life of the motor.

The axial position of the magnets 24 in the frame relative to the core28 determines the magnitude of the biasing force on the frame bearingwhich axially stabilizes the armature between the two bearing means.

In order to minimize noise related to the interaction of the NYLATRONplastic washer 164 and the sleeve bearing 228, the surface of thebearing 228 in direct contact with the washer 164 is bevelled,preferably four (4) degrees, so that any noise generated thereby isreduced at the bearing washer interface due to contact slippage betweenthe bearing and the washer during shaft rotation. Under heavy axial loadthe thrust washers conform to the bearing surface to maintain a constantpressure.

Brush Plate Assembly

As shown in FIGS. 1, 2A and 7-9B, the brush plate assembly meansutilized with the illustrated motor 20 comprises a brush plate 176preferably made of insulating material such as plastic or preferablylaminated phenolic having a plurality of generally D-shaped slots orD-slots 178 precisely formed therein and at least three isolatorattachment means 180 for receiving isolators 94 which are operativelyconnected to the frame 22. At least two brush boxes 42, 44 areoperatively connected to the brush plate 176 via the plurality ofD-slots 178. A pair of brushes 48 are inserted into the brush boxes andare each urged toward the commutator means 38 by a ribbon spring 50. Aconnecting means or copper wire (pigtail) 205 connects each brush 48 tothe electrical conducting means or plug 98.

In the presently preferred embodiment of the brush plate assembly 40 ofthe illustrated motor 20, the brush boxes 42, 44 are basicallyrectangular in shape having two walls or sides 182, 184 and a topsurface 186. While, as shown, the brush plate 176 serves as the bottomsurface of each box 42, 44, it is anticipated that each box 42, 44 couldhave its own integral bottom portion.

Because the relative location between the brushes 48 and the commutatorring 148 is critical to noise reduction and the smooth and efficientoperation of the motor itself, the positioning of the brush boxes 42, 44on the plate 176 takes on an added importance. Since the brushes canrattle, move around or become hung up in the box, thereby generatingincreased noise or resulting in motor malfunctions, the assembly andpositioning of the brush boxes 42, 44 on the plate 176 is critical.

As shown in FIGS. 7, 8A, and 8B, the brush boxes are preciselydimensioned and preferably have at least four (4) members or taperedtabs 188 for insertion into the precisely positioned D-slots 178 on theplate 176. The members 188 are then positioned on the plate 176 byholding the brush box 42, 44 in a predetermined position in such a waythat the members 188 first bend over the straight portion 190 of theD-slot and then are crimped without applying stresses on the plate 176itself. Specifically, the portions of the member 188 most proximate theplate 176 are not in frictional contact therewith because during thecrimping process, means are inserted between the tips 192 and the platesurface for preventing direct contact between the plate 176 and themembers tip 192 such that surface frictional contact between the members188 and the plate 176 is not made. Additionally, during the crimpingprocess, means are inserted into the brush box to maintain thedimensional integrity of the box while the members 188 are beingcrimped. This prevents the pulling of the box further down into theplate 176 and preventing the distortion of the axial length of the boxat either end and keeps the boxes aligned with each other.

The plurality (preferably four) of members 188 for inserting through theD-slots 178 on the brush plate 176 extend from the bottom of the twosides 182, 184. These members 188 are effectively connected to the plate176 in order to accurately position the brush boxes on the plate 176without stressing the plate 176. This is accomplished by the taperedshape of the members 188 in that the tips 192 of the members 188 aremore narrow than the upper portion 193 which is more proximate the walls182, 184. Therefore, when the members 188 are inserted into the D-slots178, the tips 192 pass through without penetrating or contacting theplate 176 but when finally positioned, at least a portion of the entiretapered portion does contact the bottom surface or opposite face of theplate 176 and at least partially penetrates the top surface or oppositeface of the plate 176.

The above provides for the precise location of each brush box 42, 44 onthe plate 176 without stressing the plate 176 due to the subsequentcrimping of the members 188 so that there is minimal, if any, frictionalcontact between the surfaces of the members closest the bottom surfaceof the plate and the bottom surface of the plate. In other words, themembers 188 are crimped in a manner to accurately, precisely, locate thebrush boxes 42, 44 on the plate 176 without applying forces in excess ofthose required to maintain the brush box position while at the same timemaintaining the internal dimensions of the brush box so that the brushwill neither rattle excessively due to a loose fit thereof or hang updue to a tight fit therein.

Extending at approximately a 90 degree angle from the two sides of eachbrush box are extensions 194 which are cutout portions of the brush boxsides 182, 184 rolled back leaving a pair of slots 196 for locating andsupporting the coils 198 of the ribbon spring means 50.

While not shown, it is anticipated that other locating means such as anextension or a post on the plate for receiving the ribbon coils 198could be utilized to position the ribbon springs on the plate.

A slot 200 is formed in the top wall of each brush box 42, 44 forreceiving the connecting means 180 for each brush means 48 which is thenconnected to the conducting means 98.

As can be seen in FIG. 8B, in order to minimize debris, such as carbondust from building up in the brush box in the areas adjacent to thebrush box or between the brush and the brush box, the brush box utilizedin the motor has neither a front nor a back wall. Additionally, the sidewalls of the brush box have middle sections 202, 204 roughlycorresponding to the extensions 194 which provide passageways on bothsides of the brush when assembled into the brush box. These passagewaysprovide space to receive the ribbon spring and, when combined with theopen rear section of the box brush, provide for the elimination ofexcessive carbon build up or other residue which might interfere withthe operable movement of the brush within the brush box. Perhaps moreimportantly, the sections 202, 204 stiffen each box to minimizevibration and thereby minimize noise.

The junctures of the left wall 184 and right wall 182 of each brush boxwith the top wall 186 are of such precision dimension that the brush 48is held in a relatively fixed position relative to the commutator 38.Also, once the members 188 of the left wall 184 and right wall 182 sidewalls are properly positioned within the D-slots 178, clearance isprovided between the brush box sides and the brush so that the brush canmove freely within the brush box while retaining a rather preciseposition relative to the commutator.

As with various other components of the motor of the present invention,various parameters can be varied to reach an optimal combination andsub-combination. In the case of the brush plate assembly, the radiallength of the brush box, axial clearance with the brush, angularclearance with the brush, radial tilt of the brush box (leading ortrailing design), distance from the commutator side of the box to thecore, length of the brush box as compared to the brush, plate and boxmaterials and thickness, boxed plate mounting technique, box to shuntclearance, brush key transfer (box orientation and location), sizing forcorrect electrical load (amps/square inch), isolator materials,durometer and location for vibration isolation and brush plate location,brush axis relative to the magnet axis, and brush shift are among thedimensions and parameters which were considered to arrive at thespecific design of the motor of the present invention.

If each brush box were to be integrally formed with the brush plate,there would be passageways formed therein similar to those of theseparate brush box illustrated. It is believed that such a new brushbox, without the extensions 194, and having four sides, such that bottomwall would not be the plate 176, would provide a more tightly or bettercontrol of the box than the design illustrated in FIGS. 8A and 8B. Thespring rather than fitting in the slot would be retained in place byposts on the plate itself.

In the illustrated brush box, it is important that the heat which isgenerated by the interaction of the brush and the commutator be radiatedso that it can be transmitted into adjacent areas thereto or intoambient space. Because plastic is a heat insulator, metal is presentlythe preferred brush box material. However, any material which wouldprovide the necessary precise sizing and allow for heat radiation anddissipation would be acceptable.

Brush

FIGS. 1, 2A, 9A and 9B show the brush means 48 of the illustrated motor.The brush means 48 preferably comprises a copper graphite blend. Thebrush means 48 when inserted into each brush box 42, 44 are eachoperatively urged out of each brush box 42, 44 by the ribbon springmeans 50 which provides a nearly constant tension/force on each brush 48against the commutator means 38 throughout the life of each brush. Thisconstant force is believed due to the curvature of the ribbon springcoils 198.

The brush means 48 are generally rectangular in shape. The commutatorcontract or engagement end 206 of the brush means 48 whichperpendicularly contacts the commutator means 38 is bevelled and thusinitially has one end portion 208 longer then the other portion 210. Thebevel 212 is located on the back side so that moment of the force aboutthe point of the isolator 94 is minimized, otherwise the plate 176 wouldtend to bow. The bevels of the opposing brushes are ground therein inopposite directions to provide smoother interaction between the brushesand the commutator and therefore generate less noise.

With the present brush design, one brush deposits residue on thecommutator and the other brush scrapes it off or removes it from thecommutator, thereby reducing noise generated by the commutator-brushinteraction.

As shown in FIGS. 1, 9A and 9B, the conducting means or copper pigtail205 is connected to the brush 48 such that when the brush is insertedinto a brush box, the pigtail 205 fits in slot 200. The composition andsize of the pigtail is selected to provide a very low resistance path sothat it will not burn if it becomes over heated and will act as a heattransfer means for transferring excessive heat from the brushes to otherareas where the heat can be better dissipated. Because the brushes getvery hot from fictional forces and resistive loss and in order toprevent the brush box and the brush plate assembly as a whole from overheating, there is a need for a means for transferring this excess heatand the pig tails 205, in addition to conducting the current, conductsome heat away from those aforementioned motor portions.

Since the ribbon spring means 80 acts with a nearly constant force, inorder to rapidly seat the brush means 48, the bevelled end portion 206,which initially contacts the commutator means 38, is slightly extended.This develops a very high initial pressure between the brush surface andthe commutator surface over a relatively small area of thecommutator/brush interface thus initially providing a very high forceper unit surface area which establishes proper filming earlier.

Since the prior practice for automotive application motors was to letmechanical wear seat the brushes onto the commutator, some brushes didnot seat properly even after extended usage due to the variety of theload experience in the applications. This condition was verified byprofilometry test of numerous brushes which revealed they wore-in withseveral different radii--the intrinsic shape, along with one or tworadii worn-in during operation. These different radii were testament tothe instability of the brushes and the potential brush noise associatedwith dynamic behavior.

In order to prevent the uneven wear-in and thus eliminate the potentialfor excessive brush noise, the brush 48 is ground to near exactdimensions of the commutator. This reduces the wear-in period and brushcard vibration thereby resulting in a quieter motor.

Additionally, the brushes are specified to near net shape therebyminimizing process time after which the brush contour is ground to aline-contact configuration resulting in lower brush originating noiselevels.

It is important to have a smooth surface on the brush that willinitially contact the commutator. This insures proper wearing of thebrush on the commutator. This is accomplished by grinding the end of thebrush which contacts the commutator in order to capture the center lineof the armature so that the brushes can move to the sides of the boxesbased upon which direction that the grinding wheels turn which alwaysturn in the same direction as the commutator turns for the particularmotor being assembled.

The brush contour is such that the brush will now fit the commutator.Basically the brush is always ground with a radius slightly larger thanthe commutator so that there is contact with the commutator immediatelyin the center of the brush arc.

As shown in FIG. 9B, the brush width is the width of the span of onecommutator segment or bar 148 (see FIG. 4B) plus the two adjacentcommutator slots 154 on either side thereof. This is done to prevent thebrush edge being the pressure point such that as a slight drop isexperienced as the commutator rolls underneath it and then bounces whenthe brush edge hits the slot on the other side of the span and toprovide for adequate time to complete the commutation event defined asthe reversal of current within a coil which is being commutated by eachbrush at any given time. If the brush were to rock, this would create avibration in the brush plate 76 which would generate noise.

Since the brush is composed of softer, more porous material than thecommutator, the brush tends to--compress and flow into the commutatorslot. As long as the brush span relative to the commutator is equal toor preferably greater than the commutator span plus two commutatorslots, the lateral stability of the other brush will be improved andwill not tend to rock as much on the commutator.

Parameters of the brush which are varied in order to interact in aminimum cost maximum performance of the illustrated motor include: brushlength, width, and depth, material and composition, shunt size,location, and stiffness, contour diameter and edge taper/bevel.

Since one of the primary objectives of the present invention is toreduce motor noise, and since noise is generated between the commutatortang and the brush plate assembly brush boxes, the distance between thecommutator tang and the top of the brush boxes must be optimized so thatfan cut-off type noise is minimized. This noise occurs whenever a tangpasses by the brush box due to the air movement generated by therevolving tang hitting the box. In order to reduce this noise, the brushbox is moved a sufficient distance away so that the noise generated bythe tang rotation is either eliminated or significantly reduced but yetnot so far away that additional motor length is added either to themotor or the commutator.

Additionally, durability of the brushes enters into the equation in thatthe radial clearance between the brush boxes themselves and thecommutator is such that the brushes maintain freedom of movement withinthe box relative to the brush box but the movement of the brush back andforth relative to the commutator is minimized thereby minimizing thechances that the brush will hang up in the box by preventing the brushextending out of the brush box so far that a potentially excessive anglebetween the brush and the box is achieved.

End Shield

As shown in FIGS. 1, 2A, 10A and 10B, the end shield 54 comprises aformed piece, preferably metallic, having a plurality of stiffeningmembers 56, a plurality of connection meanders 57, 58, 59 forinterfacing with the open end 90 of the frame 22, a cutout or mountingmeans 214 for receiving the conducting means 98 and a protuberance 216for receiving a freely aligning bearing means 60. The end shield 54 isconfigured so that the connection members 57, 58, 59 mate withcomplimentary portions 84, 86, 88 of the frame 22 to complete the motorouter body shell. The end shield 54 is operatively connected to theframe 22 by preferably staking the members 217 at each end thereof (FIG.12B).

One feature of the present invention is the choice of material used toform the end shield. Since once the bearing means 60 is properly locatedin the end shield bearing socket 218, it is desirable to minimize springback, a relatively low carbon, low spring back material is utilized suchas AISI 1010 AK DQ.

As shown in FIG. 10A, the bearing socket 218 is on the inside of theprotuberance 216 and includes three lands 220, 224, 226 for interactingwith a sleeve bearing 228 of the bearing means 60. These lands 220, 222,224 and their importance to the freely aligning bearing means 60 will bediscussed in detail below.

Bearing System

One key to the freely aligning bearing means 60 of the illustrated motoris the method and material used to assemble the bearing means 60 in boththe frame bearing socket 71 and the end shield bearing socket 218.

As shown in FIGS. 1, 2A, 11A and 11B, the bearing means 60 used in theend shield 54 and in all but one application in the frame bearing socket71 is a freely aligning bearing means versus a conventional selfaligning bearing means. A freely aligning bearing is basically when thebearing 228 under very low forces will align itself to run in such aposition that a basically good, uniform clearance is developed andmaintained between the bearing journal on the shaft 32 and the bearingitself i.e., in such a position that the center line of the bearingaligns itself parallel to the shaft center line. Since it is desirablefor the motor bearing systems to require very little force to align thebearings, the less force required to properly align the bearings, themore uniform the distribution is across the oil film across the shaft 32because if the oil film is uniform, oil leakage from the bearing systemswill be minimal given a specific force load. One advantage of the freelyaligning bearing is that the lubrication leakage is greatly reduced thusincreasing bearing life.

As stated above, one key difference between conventional self aligningbearing means and the freely aligning bearing means 60 used in theillustrated motor is the material used in the retainer 230.Conventionally, spring steel has been used, but the retainer 230 of theillustrated bearing means is very stiff and strong, preferably, for theparticular motor illustrated, AISI 1010 AK DQ structural type steelwhich when formed provides a more uniform retainer shape and thus arepeatedly uniform bearing means 60.

Another key to the improved performance of the freely aligning bearingmeans 60 is the establishment of a set of known conditions in eachbearing means 60 which is held in whatever position corresponds to thosedesired conditions. This is in contrast to prior conventional bearingsystems in which the relative position of the bearing means in the endshield or frame socket is established first and whatever conditionswhich result from the relative position is locked therein. Experiencehas shown that, in conventional bearing systems, a wide variety ofconditions are locked in for the same relative position due to, amongother factors, the bearing geometry, the socket geometry, eccentricityand the retainer geometry, all of which have certain tolerances anddimensional irregularities.

The freely aligning bearing means 60 utilized with the illustrated motorcomprises a sleeve bearing 228, which is operatively positioned in thesocket 71 or 218, and a bearing retainer member 230. The configuration,as shown, is freely aligning but is prevented from rotating in that thebearing retainer 230 and the sleeve bearing 228 have a plurality ofmembers 232 in the sleeve bearing member 228 and a plurality ofcomplementary antirotation members 234 in the retainer 230 forpreventing the sleeve bearing member from rotating but not preventingthe sleeve bearing member from freely aligning.

The bearing retainer member 230 has three lands 236, 238, 240 which aremirror images of three lands 220, 222, 224 positioned in the bottom ofthe bearing socket 218, which supports the sleeve bearing. It has beendetermined by measurement that it is important that the lands 236, 238,240 on the retainer and the lands 220, 222, 224 in the end shieldbearing socket not be axially aligned in order to provide greaterbearing movement. These six lands assure that the contact area betweenthe bearing and the socket and the contact area between the bearing andthe retainer allow the bearing to easily align while maintaining thebearing position when a load is applied to the shaft. Basically the sixlands insure that there is always contact with the bearing and that theforces are distributed equally to the end shield and the retainer fromthe bearing.

The illustrated freely aligning bearing means 60 is assembled intobearing sockets 71, 218 of the frame 22 and the end shield 54respectively and then held in place by an adhesive. Once the bearingmeans 60 is placed in either socket 71, 218 with the adhesive activatoron the end shield or frame and the adhesive on the bearing retainer 230surfaces, a force designed to be sufficient to seat the bearing retainerand bearing in the socket is applied, thereafter a second fixturingforce, for establishing a slight preload is applied. During this period,the adhesive initially sets and is allowed to cure. Once the adhesivehas initially set, the bearing retainer and bearing are fixed in theprotuberance or socket having the predetermined conditions establishedby the force applied. The initial adhesive bond between the retainersurface and the socket surface is sufficient to maintain thepredetermined conditions and to enable the end shield or the frame to befurther processed while the adhesive, which retains the bearing systemtherein, is completely cured.

It is believed that the predetermined conditions are established andmaintained because the adhesive bond between the retainer and thebearing receiving means or socket freely suspends the retainer untilpreloaded and thus compensates for all the dimensional variations ineach component member such as the bearing, the bearing retainer and thebearing receiving means or socket. The bearing means is positioned inthe socket so that the bearing can align on the shaft, since the entirebearing system can float until the adhesive sets, no high contact forcesbetween the bearing and the bearing retainer are built up between thebearing and the retainer means and the adhesive fills in the gaps and isset under a predetermined force to precisely establish the predeterminedset of conditions.

In the illustrated motor, the frictional force between the bearing andthe rotating shaft is not strong enough to withstand the rotationaltorque, and the bearing 228 without antirotation tabs 234 will rotate inthe retainer 230 and wear out the outer periphery of the bearing. Thebearing is held loosely in the socket by the bearing retainer, but yettight enough to accomplish the freely aligning purpose.

The freely aligning bearing means is assembled in a socket according tothe following method. First, the socket and the bearing retainer shouldbe free of all dust, dirt and grease. An adhesive activator, such aspreferably Dymax activator 535, is applied to the effective area of theframe or end shield socket 71, 218. A bead of adhesive, such as,preferably, Dymax 628 VT adhesive, is applied around the outer diameterof the retainer 230 near the closed end. Immediately after applying thebead of Dymax 628 VT, the parts are assembled by rotating the retainerapproximately 60 degrees relative to the socket in order to mix theadhesive and the activator. An axial force of preferably approximately40 pounds is next supplied to the retainer for approximately two tothree seconds and preferably approximately 3.5 pounds of pressure forthe remainder of a five minute total initial setting time. At the end ofthe five minute period, the initially set bearing system is placed underultraviolet light for curing for approximately two minutes in order tocure any adhesive not cured by the activator.

As shown in FIG. 2B, the bearings system 60' when used in an enginecooling application is illustrated. As shown, the ball bearing member228' is positioned in the bearing socket 71 and then is staked inposition and retained therein by four tabs 231 staked at a thirty (30)degree (plus or minus 5) angle relative to the internal wall of theprotuberance 68.

When locking the ball bearing in position in the bearing socket, it isimportant that all four tabs 231 are staked simultaneously to insure noradial or axial movement of the bearing and bearing retainer. As withthe freely aligning bearing of the present invention, in staking thebearing retainer 230' into position is pressure sensitive as opposed totravel sensitive thus a certain amount of force is exerted on the ballbearing and retainer prior to the staking occurring. This operation, hasa similar effect as the pressure applied to the sleeve bearing 248 ofthe freely aligning bearing means 60 which is adhesively maintained inthe bearing socket. After staking, a push test comprising a 5 poundaxial force is applied to the inner face of the ball bearing toward theopen end of the frame in order to insure that the staking process hasbeen effective.

Mounting Flange

As shown in FIGS. 1, 12A and 12B, two representative examples ofmounting flanges 64, 64' of the plurality of mounting flanges used withthe motor of the present invention is operatively connected to the frame22 by an adhesive. Each mounting flange 64, 64' is the only component ofthe motor which is presently unique to each application. Specifically,at present, each structure to which the illustrated motor is connectedis different, thus necessitating a different mounting flange for eachapplication.

In general, each mounting flange is a formed metal part, with somehaving a plurality of stiffening ribs 66 (FIGS. 12A and 12B) formedtherein for raising the low natural vibration frequency of the metal sothat the structural noise is reduced.

The mounting flange 64, (engine cooling applications) or 64' (airconditioning or heater applications) comprises a mounting portion 242having a plurality of mounting apertures or mounting means 244 formedtherein and a cupped shaped portion 246 formed circumferentially arounda center aperture 248 in which the frame 22 is received. This cup shapedportion 246 has a greater radius from the center of the aperture 248 atone end 250, i.e. an upper end of the cup shaped portion, and graduallytapers down to a smaller radius at the point 252, i.e. a lower end ofthe cup shaped portion, which is approximately the circumference offrame 22 (FIG. 12A).

One feature of the present frame-flange connection is the unique mannerin which each flange 64, 64' is connected to the frame 22. As shown inFIG. 12A, when assembled onto the frame 22, a reservoir 254 (FIG. 12A)for receiving the adhesive is formed between the outer surface 256 ofthe frame 22 and the inner surface 258 of the cup shaped portion 246 ofthe mounting flanges 64, 64'. This particular construction provides forthe retention of the adhesive in the reservoir during the rotation ofthe frame relative to the cup shaped portion 246 during themanufacturing process for connecting each mounting flange 64, 64' to themotor frame and for curing the adhesive.

A frame alignment means 260 is operatively positioned on each flange 64,64' for properly aligning the flange relative to the frame 22 for eachparticular application. This insures that each mounting means 224 isproperly positioned for each application.

During this assembly operation, the outer surface 256 of the frame 22and/or the inner surface 258 of the flange cup shaped portion 246 haveadhesive activator applied thereon. When rotated with respect to eachother after the adhesive is inserted into the reservoir, adhesivecontact between the surface area of the outer surface of the motor frameadjacent the inner surface of the flange cup is effectuated. Aftercuring, the adhesive bond therebetween has proven to be quitesatisfactory.

During the mounting of the flange to the frame, the frame and the flangesurfaces are cleaned of contaminants and after the adhesive activator,such as preferably DYMAX activator 535, is applied to the inner diameterof the flange and the specific area where the flange will be mounted onthe outer diameter of the frame, sufficient time is provided for thesolvents and the activator to evaporate. Next, a bead of adhesive, suchas preferably DYMAX 602 gel, is applied to the frame at the point wherethe skirt of the flange cup shaped portion will stop. Immediately afterthe application of the bead of adhesive, the flange is assembled to theframe which is rotated and moved axially into final position by rotatingthe flange approximately 90 degrees relative to the frame in order tomix the activator and the adhesive after which they are maintained inthe rotating fixture in the proper relative position for the specificapplication for a time sufficient to allow the combinedactivator-adhesive to initially set, preferably approximately threeminutes. Thereafter, the combined assembly is placed under a curing lampin order to cure the adhesive not cured by the activator.

While the products and processes herein described constitute preferredembodiments of this invention, it is to be understood that the inventionis not limited to these precise products and processes, and that changesmay be made therein without departing from the scope of the inventionwhich is defined in the appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:
 1. An axial vibration reduction system for an electricmotor having magnet means mounted in a frame, an armature having alamination core mounted on a shaft and two bearing means operativelypositioned relative to the shaft, the axial vibration reduction systemcomprising:resilient means, operatively positioned on the shaftproximate each bearing means, for resisting movement of the armaturerelative to the frame, the armature being positioned in the frame suchthat the lamination core is not axially centered relative to the magnetmeans whereby a force is generated on the resilient means most proximatean end of the lamination core closest an axial center of the magnetmeans.
 2. The axial vibration reduction system of claim 1 wherein theresilient means further comprises:at least one elastomeric washer and atleast one NYLATRON plastic washer, the NYLATRON plastic washer being incontact with the bearing means.
 3. The axial vibration reduction systemof the previous claim 2 wherein the bearing means includes a beveledsurface contacting the NYLATRON washer and having the force appliedthereto.
 4. The axial vibration reduction system of claim 3 wherein thebearing means surface contracting the NYLATRON plastic washer is beveledat four (4) degrees.